The exclusive event, hosted by a Florida developer on his yacht "Cracker Bay," was one of a dozen exclusive events meant to nurture those who have raised more than $1 million for Romney's bid.

"I think it's ironic they do this aboard a yacht that doesn't even pay its taxes," said a woman who lives aboard a much smaller boat moored at the St. Petersburg Municipal Marina.

Romney's Cayman-based investments have come under fire during the campaign.

The event, attended by no more than 50 people, along with Romney's relatives, including older brother Scott, appeared on no public calendars. ABC News obtained a schedule of the Romney campaign's "Victory Council" and waited dockside to speak with members.

"It was a really nice event. These are good supporters," said billionaire Wilbur Ross, an energy industry executive.

Spencer Zwick, one of Romney's top fundraisers, said the event was not to raise money, but simply to thank donors.

Virginia Gov. Bob McDonnell was scheduled to speak.

The Cracker Bay is owned by Gary Morse, developer of the Villages retirement community. Companies controlled by Morse gave nearly $1 million to the pro-Romney Restore Our Future superPAC. Registered in the Caymans, the Cracker Bay has an impressive art collection and can seat 30 for dinner.

Romney to date has declined to identify the names of his top "bundlers" -- those who gather checks from scores of donors on the candidate's behalf.

"He is the first nominee in 12 years to withhold these names," said Sheila Krumholz, executive director of the Center for Responsive Politics, which tracks political money on the website opensecrets.org.

"These are the most important insiders," she said. "The public needs to know who these people are because they are the ones who stand to gain the most from a Romney presidency."

Her group and others have gathered more than 20,000 signatures from people calling on Romney to name his top bundlers.

Campaign officials at the event declined to comment. "I think Gov. Romney is going to do what he has to, to follow the law," Gov. McDonnell told ABC News.

Among those attending was Mel Sembler, a former top supporter of President George W. Bush and Charlie Moncrief, an oil executive from Texas, and his wife Kit. Other guests covered up their nametags as they exited for waiting busses and SUVs to take them to their next event.

Kit Moncrief said she and her husband had pledged to raise $1 million for Romney. When asked about the fundraising, she said: "We don't like it either, but it's the system," she said.